Determined to speed up pace of play but unwilling to inflame the players union, Major League Baseball Commissioner Rob Manfred announced a set of initiatives for 2018 that includes a limit on mound visits and reduced commercial breaks between innings — but no 20-second pitch clock for 2018.

After more than a year of negotiations, the Major League Baseball Players Association refused to agree to Monday’s changes but also signed an agreement saying it will not oppose them. MLB has the right to make playing rules changes absent an agreement with one-year notice, and it made proposals during the 2016-17 offseason for a pitch clock and more restrictions on mound visits.

“I am pleased that we were able to reach an understanding with the players association,” Manfred said in a statement. “My strong preference is to continue to have ongoing dialogue with players on this topic to find mutually acceptable solutions.”

Union head Tony Clark said in an e-mail to the Associated Press, “The focus on mound visits and/or the level of commitment on the other pieces simply didn’t focus enough attention on the areas the players wanted to address — so no agreement was reached.”

The amendments to the rules include a general limit of six mound visits per nine-inning game without a pitching change, whether by a manager, coach or player.

That rule will stop frequent visits, especially by infielders.

“It’s part of my job, when the pitcher needs me, I go and tell them, calm down, breathe, need to find one spot and pitch to it,” Twins third baseman Miguel Sano said at the team’s first full-squad workout in Fort Myers, Fla. “It’s a routine I have. It’s part of the job. Maybe I don’t need to go straight to the mound if they say so. But I need to find something to do. I can help.”

Commercial breaks will be shortened and a timer will start at the end of each half-inning. Pitchers can throw as many warmup pitches as they want before the timer runs out, though they are no longer guaranteed eight warmup pitches.

“We’ll see,” Twins righthander Tyler Duffey said. “I think it will affect pitchers who take a long time, more than anything else. Hitters, I feel that some of them wait until their [walk-up] music stops. They just have to hit ‘play’ sooner and they will walk up.”

Until now, the only restriction on mound visits was that a second visit to the same pitcher during an inning by a manager or coach resulted in an automatic pitching change. The number of visits by catchers during games has increased in recent years, contributing to the average time of a nine-inning game stretching to a record 3 hours, 5 minutes last season, up from 2:46 in 2005.

Under the new rule, each team would get an additional mound visit without a pitching change for each extra inning. Trips will not count against the limit following an offensive substitution, to check on potential injuries or to clean spikes on wet fields. If a team is out of visits, the plate umpire may give permission for additional trips by the catcher in the event of a cross-up on pitch signals.

MLB is trying to keep between-inning breaks to 2 minutes, 5 seconds for most games, 2:25 for regular-season games on national television and 2:55 for tiebreaker and postseason games. There are exceptions relating to injury and if the pitcher or catcher finishes the previous half-inning on base, at bat or on deck.

Between the stagnant free-agent market this offseason and Manfred’s desire to impose rules changes to speed the game, it has been a turbulent time for MLB and the union. Manfred has been in favor of a pitch clock but agreed to hold off on that matter “in order to provide players with an opportunity to speed up the game without the use of those timers.”

Manfred still has the right to implement the clock in future seasons — with ball-strike penalties — if this year’s changes don’t improve the pace of play, but he chose a more diplomatic approach for 2018.

“Players were involved in the pace-of-game discussion from Day 1,” Clark said, “and are committed to playing a crisp and exciting brand of baseball. But they remain concerned about rule changes that could alter the outcome of games and the fabric of the game itself — now or in the future.”